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(888) 868-2900 | Both processes are chemically based methods of improving the surface of stainless steel — but they differ in efficacy, metal compatibility, precision, impact on roughness average (Ra), and cost.
Passivation cleans and protects. Electropolishing removes, improves — and passivates.
Surface imperfections left behind by machining and welding — from free iron to burrs to microcracks — can compromise the fit, function and corrosion resistance of stainless steel parts.
Passivation removes free iron and contaminants from the part surface and builds a chromium-rich passive layer. Electropolishing removes a microscopically precise layer of surface material itself — taking burrs, microcracks and embedded contaminants with it, and leaving the part passivated in the same step.
Watch: how electropolishing and passivation differ, and when to choose each.
How the two processes compare on the criteria that matter for your parts.
| Criterion | Passivation | Electropolishing |
|---|---|---|
| Removes surface contaminants | Yes — free iron and foreign material | Yes — plus embedded contaminants |
| Removes base material | No | Yes — microscopically precise, +/- .0001″ – .0005″ |
| Removes burrs & microcracks | No | Yes |
| Surface finish (Ra) | No change | Up to 50% improvement |
| Removes weld heat tint & scale | No — not effective in the heat affected zone | Yes |
| Improves fatigue life | No | Yes |
| Corrosion resistance | Improved | 30X greater than passivation aloneSee 888-hour salt spray proof ↓ |
| Leaves part passivated | Yes | Yes — no separate passivation step needed |
| Alloy compatibility | Stainless steel & refractory metals; flash attack risk on low chromium/nickel alloys | Effective for nearly all metal alloys |
| Processing | Bulk baskets — cost-effective for volume | Custom racking — consistent part-to-part results |
| Extremely tight tolerances (<.0002″) | Suitable — no material removed | May not be suitable |
Independent ASTM B-117 salt spray testing — electropolished vs. passivated vs. raw.
Sample panels of 304, 410, 420 and Trinamet stainless steel were submitted to an independent testing facility for ASTM B-117 salt spray exposure, in raw, passivated-only and electropolished states.
Electropolished parts have 30 times the corrosion resistance of parts that are passivated only. The results below show the difference at 24 hours and 888 hours of exposure.
Photography from independent ASTM B-117 salt spray testing at an accredited outside laboratory.
144 hours of ASTM B-117 salt spray — raw, passivated and electropolished.
A wire weldment fabricated from 304 stainless steel was submitted to ASTM B-117 salt spray testing at an independent testing facility, in the raw, passivated and electropolished state.
After 72 hours of exposure to the salt spray, the raw and passivated wire weldments developed red corrosion in the resistance welded areas. The electropolished part is rust free. Electropolishing is effective in treating the carbide precipitation condition that occurs in the heat-affected zone during welding. It also improves the chrome to iron ratio on the surface, which greatly improves corrosion resistance.
Deburred, polished, cleaned and passivated in one pass. Electropolishing can eliminate the separate deburring, polishing, cleaning and passivation steps a part would otherwise need.
Precision surface material removal that improves fit, function and lifespan.
Electropolished parts have 30 times the corrosion resistance of parts that are passivated only — verified in independent ASTM B-117 salt spray testing.
Precise removal of surface material eliminates the imperfections that become initiation sites for corrosion, fatigue failure and pathogens.
A smoother, brighter surface that enhances cleanability and appearance — with antimicrobial benefits for medical and food processing applications.
One limitation: because electropolishing removes surface material, it may not be suitable for parts with extremely tight tolerances that cannot accommodate at least .0002″ of material removal.
A proven, cost-effective cleaning process for stainless steel.
Removing free iron and building a chromium-rich passive layer improves corrosion resistance and extends part lifespan.
Because passivation removes no base material, it’s suitable for parts with extremely tight dimensional tolerances.
Parts are processed in baskets in nitric or citric acid formulations — an economical option for high-volume cleaning.
One limitation: metals with lower levels of chromium and nickel are susceptible to flash attack during passivation, which can weaken the base material — and passivation cannot remove scale or discoloration in the heat affected zone of welded components.
Electropolishing combines a chemical bath with an electric current that precisely removes a uniform layer of surface material. Acting like lightning, it removes the high points first — stripping away contaminants and microscopic imperfections such as cracks, burrs and jagged edges, and resulting in an evenly smooth, bright surface.
During passivation, stainless steel parts are submerged in a nitric or citric acid bath. Acid concentration, temperature and time are adjusted by alloy to remove free iron and other contaminants and create a chromium-rich, passive surface layer that improves corrosion resistance.
The best way to determine if electropolishing is the best solution for your part is to send us a sample. We’ll electropolish it for free and send it back to you in a few days.
From implantable devices to surgical instruments, electropolishing is a single-process treatment that results in biocompatible, safe and ultra clean parts.
We offer aerospace vendors and original equipment manufacturers our signature metal finishing services to increase fatigue-resistance for their metal parts, rendering them capable of withstanding the stress and corrosion that comes with long-term use.
Our strict adherence to industry standards ensures that pharmaceutical components are electropolished in accordance with ASTM B912 and ASME BPE specifications. These products are clean and smooth, corrosion resistant and contaminant free.
Corrosion resistance and microfinish improvement are essential for critical automotive parts, making electropolishing an increasingly beneficial option for automakers.
Our metal finishing services help increase corrosion resistance for these parts, and by removing the outermost layer of metal withelectropolishing the durability and longevity of these appliance components is increased.
Electropolishing materials for this industry eliminates the buildup of bacterial biofilms, as well as keeping the equipment free of contaminants like Salmonella. Electropolishing delivers the level of sanitation required by a number of regulatory agencies.
From robotics to mobile equipment, the uses of electropolishing in the hydraulics and pneumatics industry are many. By helping prevent premature part failure, electropolishing reduces downtime and increases the life cycle of these components.
Improving conductivity and performance is just one benefit electropolishing offers for electronics parts. The surface finish is improved by as much as 50%, removing imperfections from the material without material removal.
The extreme heat resistance and resilience characteristic of refractory metals like niobium, molybdenum, tungsten, tantalum and TZM make them useful in applications like aerospace components, small modular reactor components and other parts that must withstand extreme environments.
A wide array of modern assemblies for everything from aerospace parts to medical devices depend on high-quality springs that must perform to incredibly precise specifications, often in very tiny spaces.
Small modular reactors are entering component fabrication under tight schedule pressure. Across every coolant technology, surface integrity is becoming a qualification gate — not an afterthought.
Electropolishing is a precise and controllable process for eliminating defects from the surface of metal parts. But it’s not the only finishing process available to manufacturers; there are mechanical, chemical and plating processes that can remove defects and improve the…